The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
A conventional sight glass assembly may be mounted to, for example, a process tube or vessel to allow a person to view the contents (for example, fluids) inside the process tube. The sight glass assembly generally includes a glass and a metallic ring around the glass. The glass may be fused or sealed to the metallic ring. The metallic ring protects the glass therein. The sight glass assembly is mounted to the process tube by welding or brazing the metallic ring to the process tube.
Materials for the conventional sight glass and/or hermetic terminal assemblies are limited due to difficulty in joining the glass, the metallic ring, the conductor, and the process tube. In high pressure applications, the glass is generally fused to the metallic ring to form a hermetic seal there between at elevated temperatures. The metallic ring is generally required to have a high melting point to avoid rapid oxidation at the elevated temperatures. Moreover, the metallic ring is generally made of a weldable metal to allow for joining of the metallic ring to the process tube.
Laser welding may also be used to join the metallic ring to the process tube. Laser-welding requires particular skills and care to avoid generating heat shocks to the hermetic terminal assembly. Therefore, mounting the conventional sight glass and/or hermetic terminal assemblies to the process tube is time consuming and is relatively expensive.